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Thread: BT Paper insulated wiring?!

  1. #1
    Automated Home Sr Member danward79's Avatar
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    Default BT Paper insulated wiring?!

    Hi,

    I have just moved into my new flat, and have started my wiring install.

    I have come across some old, very old BT wiring which comes into the flat and is still in use. It is paper insulated, i.e. the paper is just twisted around the conductors, it would seem in two layers.

    The second layer is marked with a "II" on two of the wires and a "I" on two, I assume for two lines? I can not see which of the two is supposed to be the "A" or "B" wire, in each pair.

    Has anyone come across this before? Any ideas / tips?
    Cheers

    Dan

  2. #2

    Default Re: BT Paper insulated wiring?!

    Quote Originally Posted by danward79
    I have come across some old, very old BT wiring which comes into the flat and is still in use. It is paper insulated, i.e. the paper is just twisted around the conductors, it would seem in two layers.

    The second layer is marked with a "II" on two of the wires and a "I" on two, I assume for two lines? I can not see which of the two is supposed to be the "A" or "B" wire, in each pair.

    Has anyone come across this before? Any ideas / tips?
    Does this cable have a lead sheath ?

    The only paper insulated cable I have ever seen was lead sheathed.

    There are some underground cables that are filled with grease to keep water out but these have plastic insulated conductors. These contain a spirally wrapped paper or plastic tape which indicates which layer of the cable you are working on.

    A 5 pair cable would have a single Orange/White pair on the inner layer. The next layer would have Orange/White as the first pair, then Red/Slate, Blue/Brown, Green/Black.

    Larger cables use a similar scheme where the first pair on a layer is always Orange/White and the last pair is Green/Black. Irrespective of the number of pairs in the layer, the pairs between first and last alternate between Red/Slate, Blue/Brown.

    Whatever the construction of the incoming cable, that is not an area that you should be working on. The cable upto the NTE (Network Termination Equipment) belongs to the Telco whether it is BT or any other operator. The only bit you should be working on is AFTER the NTE.

    If you dont have an NTE anywhere in the house then I would assume that there is a hardwired phone somewhere in which case you need to get BT in to remove the phone and give you an NTE/Linebox. If the cable really is that old and decrepid then it will almost certainly be replaced.

    Hope that helps

    Keith
    www.kat5.tv

  3. #3
    Automated Home Sr Member danward79's Avatar
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    Default Re: BT Paper insulated wiring?!

    Hi Keith,

    Yeah it has a lead outter. To give you some idea, the block of flats I live in was built in 1938, so I would not be surprised if it is of that era.

    The cable it's self only has 4 cores, (2-pairs).

    It is not an NTE box, as you say I think it is hard wired to the exchange?

    I will give them a call some time. However I don't know what they will say as I don't subscribe to them!
    Cheers

    Dan

  4. #4

    Default Re: BT Paper insulated wiring?!

    Quote Originally Posted by danward79
    Hi Keith,

    Yeah it has a lead outer. To give you some idea, the block of flats I live in was built in 1938, so I would not be surprised if it is of that era.
    I should have been a detective :-)

    Quote Originally Posted by danward79
    The cable it's self only has 4 cores, (2-pairs).

    It is not an NTE box, as you say I think it is hard wired to the exchange?

    I will give them a call some time. However I don't know what they will say as I don't subscribe to them!
    Given the age of it, the first block it gets to inside the flat is probably black bakelite about 2" x 4" with 4 sets of terminals. Internal cable of the era would have been cotton covered with rubber insulation on the conductors and probably only 3 wires - Blue, Orange, Green.

    Presumably you are getting telephone service from some other company via this cable then. I dont know the ins and outs of LLU (Local Loop Unbundling) where other operators use BT's infastructure to connect your house to their equipment in BT's exchange but I would imagine the model is similar to that used for Gas or Electricity. Irrespective of who you actually pay for your gas, the infrastucture remains the property of Transco and they deal with all maintenance outside upto your meter.

    If the cable went faulty it would have to be replaced. One of the big problems with Lead/Paper cable is damp. Provided the lead sheath is in good condition then everything is fine but if the sheath cracks or corrodes then moisture can get in and the line goes down.

    Your cable is probably attached to the wall using "Lead Lugs" which are a heavy square nail with a lead lug atached which is bent over the cable to hold it in place. If the cable were to be flexed slightly where it is clipped in place the sheath would almost certainly crack and when it rained the moisture would get in and cause the cable to fail.

    Regards

    Keith

  5. #5
    Automated Home Sr Member danward79's Avatar
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    Default Re: BT Paper insulated wiring?!

    The terminal block is not bakerlite, but is plastic, about 2" x 1.25" ish... It does have 4 pairs of screw terminals thou.

    I actually get my phone thru NTL, totally different infrastructure.

    The only reason I want to connect the BT stuff to my patch panel is "just in-case" I want to use a BT phone or the next people in the flat do.

    In terms of the flats wiring it "was" (til I snipped it all away!) Green/White connected to terminal 2, and White/Green connected to 5.

    At the connection box, non of the terminals were in use! The new wiring was tapped with insulation tape and twisted together... :evil: :evil: :evil:

    The terminal 3's were connected with a white/blue wire also taped together.

    As yet I have not found the lead lugs you refer to, I do know the type you mean thou. I am sure I have not looked far enough.

    Do you think the wiring is dangerous? The paper is dry as a bone from what I can see.
    Cheers

    Dan

  6. #6

    Default Re: BT Paper insulated wiring?!

    Quote Originally Posted by danward79
    The terminal block is not bakerlite, but is plastic, about 2" x 1.25" ish... It does have 4 pairs of screw terminals thou.
    That'll be a BT52A then if it is slightly rounded.

    Quote Originally Posted by danward79
    I actually get my phone thru NTL, totally different infrastructure.

    The only reason I want to connect the BT stuff to my patch panel is "just in-case" I want to use a BT phone or the next people in the flat do.
    Ah! I see :-)

    Quote Originally Posted by danward79
    In terms of the flats wiring it "was" (til I snipped it all away!) Green/White connected to terminal 2, and White/Green connected to 5.

    At the connection box, non of the terminals were in use! The new wiring was tapped with insulation tape and twisted together... :evil: :evil: :evil:

    The terminal 3's were connected with a white/blue wire also taped together.
    In that case, assuming you want a nice neat job with nothing showing, what I would do is this.....

    1. if the cable comes in via a window or dorr frame, follow the route of the incoming cable to a point where you could place a single gang box inside the house.

    2. cut out a hole for a deep single gang box and drill through to the outside (POINTING DOWNWARDS!!!) so that you can feed the lead sheathed cable in from outside.

    3. Run a CAT5 cable from the same box to your Node 0 or wherever you intend to deliver the potential phone line to.

    4. Buy an NTE5 http://www.solwise.co.uk/telesun.htm

    5. Connect the lead sheathed cable to A and B on the rear of the NTE5.

    6. Connect the
    BLUE/White of the CAT5 to "2"
    WHITE/Blue to "5"
    ORANGE/White to "3"
    on the removeable faceplate

    Dont worry about getting the right two wires as it wont be connected at the other end and if telephone service is ever reconnected BT will test it to make sure it works OK and in all probability will renew the external cable anyway.

    The reason I suggest installing an NTE5 is so that you end up with a neat installation with the NTE where you would prefer it.

    As an alternative to 4,5,6. You could just fit the existing block into back box and fit a blank faceplate but for under a fiver you may as well do a "proper[ish] job" :-)


    Quote Originally Posted by danward79
    Do you think the wiring is dangerous? The paper is dry as a bone from what I can see.
    There will be nothing connected so the only danger is from lead poisoning if you decide to chew the cable !! :-) :-)

    Hope that helps

    Keith

  7. #7
    Automated Home Sr Member danward79's Avatar
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    Default

    You have basically summarise what I have done already, Thanks.

    It actually comes up thru the building somewhere... and ends up in my airing cupboard. I have reterminated the block and wired it as you suggest, with cat 5.

    The only difference is I was going to connect the master socket up in the node 0 near the patch panel. I was also going to provision in you "Silent Phones" trick.

    Thanks for all the anwsers.
    Cheers

    Dan

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